Well...
Mine comes tomorrow like rest of the country.
Lets be honest, you're not seriously going to be using one of these *instead* of a mouse, or a keyboard, you're going to be using it in concert with one.
Say you're a 3d artist. You're going to want to use your left hand to move whatever the object is or the view port and do some gestures and use your mouse to actually do the work so to speak. If it's photoshop you're working with you're gonna want gestures to change tools, handle zoom and stuff like than and save the fine detail for the mouse or pen. Same goes for gaming and whatever else you can think of.
It's early days yet, both users and developers aren't going to know at this point what to do with it, especially with Leap being so blasée about release dates (some of us wanted the thing early so we could be inspired to write some software for it and didn't want the laggy alpha units to play with but apparently Leap wanted time to get software out which I - and many others - informed them via twitter and other media in no uncertain terms was a dumb idea).
The important questions right now are a) is it accurate and b) is it as described - ignoring all the what comes next question. Right now we're at the point we should have been at back in May.
As for the tiredness stuff - some of use who sit at our desks all day could use a little exercise - but I'm thinking elbow on desk?